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Dec. 12, 1967 N. D. MANOR ETA!- 3,358,274

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MAGNETIC com: MEMORY MATRIX Original Filed Dec. l5. 1959 14 Sheets-Sheet 1 FALSE 0) United States Patent 3,358,274 MAGNETEC CORE MEMQRY MATRIX Neil B. Manor, Xenia, and James H. Randail, Dayton,

Ohio, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland (Eriginal application Bee. 15, 1959, fier. No. 859,598, new Patent N 0. 3,112,394, dated Nov. 26, 1963. Divided and this application Oct. 7, 1963, Ser. No. 314,096

2 Claims. (Cl. 340-174) ABSTRAT SF THE DESCLOSURE A memory system which takes advantages of the fact that if the core is full-selected in one direction and then is half-selected two or more times in the opposite direction, then the first noise pulse generated as a result of the first half-select pulse is substantially greater (approximately 10 times) than the subsequent noise pulses generated as a result of the subsequent half-select pulses. Such advantage is taken simply by insuring that the largeamplitude noise pulse generated by the first half-select read pulse is generated before the actual reading operation starts with respect to a particular core and is thereby ignored.

The present application is a division of copending application Ser. No. 859,598, filed December 15, 1959, and now US. Patent No. 3,112,394, by P. B. Close et al., and assigned to the same assignee as the present divisional application.

The features of the present invention which are believed to be novel are set forth with particularity in appended claims. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference characters identify like elements, and in which:

FIGS. 1A and 1B, when joined together at the dashed lines, form a simplified block diagram of the computer circuitry;

FIGS. 2A and 28, when joined at the dashed lines, form a schematic circuit diagram of the coincident current magnetic core memory;

FIG. 3 is a portion of the logical diagram of the readwrite, digit-cycle, word-cycle and subcommand initiating circuitry;

FIG. 4 is an additional portion of the logical diagram of the read-write, digit-cycle, word-cycle and subcommand initiating circuitry;

FIG. 5 is a logical diagram of the bit-counter;

PEG. 6 is a logical diagram of the digit-counter;

FIG. 7 is a logical diagram of a high-order section of the word-selecting register;

FIG. 8 is a logical diagram of the low-order section of the word-selecting register and a logical diagram of the Y-drivers;

FIG. 9 is a logical diagram of the X and Y grounders;

FIG. 10A is a logical diagram of the memory sense amplifiers;

FIG. 10B is a logical diagram of the rack-readout circuitry;

FIG. 11A is a timing chart illustrating the instantaneous logical states of the various control lines utilized during a memory read-write cycle of operation;

PIG. 11B is a timing chart illustrating the instantaneous logical states of the various synchronizing clock lines.

In accordance with the present invention, there has been provided a novel memory for storing binary information and which comprises a multiplicity of toroidallyshaped cores which possess a substantially square magnetic hysteresis-loop characteristic. Each core has an outside diameter of .080 inch and an inner diameter of .050 inch, and is approximately .025 inch thick. It is well known to those skilled in the art that, due to the fact that the ferrite core possesses a substantially square hysteresis-loop characteristic, it therefore has two stable states of magnetic remanence, each of which is respectively indicative of a binary one and a binary zero. If a current-carrying conductor is threaded through the hole in the core, current in one direction through the conductor causes the core to be permanently magnetized in one direction, whereas current flow in the opposite direction through the conductor causes the core to be permanently magnetized in the opposite direction. Thus, a core is permanently magnetized in one direction or the other, depending upon the direction of current flow in the conductor threaded through the hole in the core. To summarize, when a core is magnetized in one direction, it represents a binary one, and when the core is magnetized in the other direction is represents a binary zero. Four cores are utilized as a group to collectively represent a single decimal digit, although, with the use of the binary form of notation, each group of four cores could possibly represent a number from O to 15. However,

in the present computer, only the numbers 0 through 9 are actually stored in the memory.

In order to reverse the magnetic remanence of the core from a binary one to a binary zero notation, or from a binary zero to a binary one by reversing the direction of magnetization thereof, a magnetomotive force of approximately three hundred and sixty milliarnpere turns is required at 25 degrees centigrade. This is obtained by the equivalent of passing 360 milliamperes of current through a single conductor threaded through the aperture of the core. A magnetomotive force of one half this value-4e, milliampere-turns-does not appreciably disturb the magnetic remanence of the core.

After a core has been magnetized in a predetermined direction to represent a binary one or a binary zero, it remains in that state of magnetic remanence indefinitely. The magnetic remanence state of the core is reversed only by a full-amplitude current impulse passing through the conductor threaded through the core. However, at certain predetermined times, it is necessary to read or determine the state of magnetic remanence of each core. Therefore, an additional conductor or sense wire is also threaded through the core aperture, so that, whenever the magnetic state of the core is changed from a binary zero to a binary one representation, or from a binary one to a binary zero representation, a voltage impulse is induced in the sense wire indicative of the reversal of magnetic remanence of the core. Thus it is seen that an impulse is induced in the sense wire only when the magnetic state of the core is reversed. In order to determine whether a particular core has been previously magnetically conditioned to represent a binary one or a binary zero, a full-amplitude current of approximately 360 milliamperes is sent through the firstmentioned conductor in a direction to set the core to a binary zero representation. However, if the core had been previously set to a binary zero representation, a voltage impulse is not induced in the sense wire. However, if the core was previously in a binary one representation, its magnetic remanent state is reversed, and, consequently, a voltage impulse is induced in the sense wire indicative of the reversal of the magnetic state of the core. After the magnetic state of the core is sensed, however, its magnetic state is immediately thereafter indicative of a binary zero representation regardless of its initial state. It is therefore necessary to restore the coreto 'itsoriginal magnetic state normally by sending a full-amplitude current impulse through the first-mew tioned conductor to set the core back to a binary one representation if the core was previously in that particularstate.

The present core memory has a capacity of one hundred ten-decimal-digit numbers which are hereinafter termed words." Due to the fact that a negative word is storedin the memory as a positive complement, there is no need'for abinary sign bit, as is conventional inmost computers. A Word is selectively stored in. the: memory incne of a hundred different locations which are called addresses andwhich are numbered'frorne b through 99..In1 addition to. the one hundred normal addresses, there. are two additional addresses labeled A and: B. The. words stored in addresses through 99 not only represent. arithmetic data, but also represent instructionswhich are utilized by, the computer to dictate the sequence ofzoperations: therein. The words previously stored. in addresses. qb through 99 of the memory may be changed by instructions given by. the computer; however, the words located in addresses. A and B are used by-the computer to store intermediate resultsduring.

arithmetic; computations and cannotbe changed: directly by instructions.

With reference to: FIGS; 2A. and 2B, there is schematically shown the ferrite core memory: utilized by the presentcomputer; Such a memory comprises four thousand and eighty type N-400-080ferritecores at present manufactured by the. assignee of. the instant application.

The. ferrite, cores. of the memory are selectively arranged in apattern of rectangularly-shaped configurationhaving one hundred two vertical columns and forty horizontalrows thereof. The first one hundred columns, as viewed. from left to. right, respectively, represent memory address! locations through 99, whereas the two remaining rightmost columns respectively represent address-locations A and B. In each of the columns, from the topmost to the bottommost core, the forty cores are arranged in a successioncf ten groups,vwith each group. containing four cores. Each. group of four cores is representative of a decimal digit of a. predetermined order, Whereas allof the groups of a particular column collectively represent all of the ordersof a word ten decimal digits'in length. Each of the ten successive decimal digits of the word located in any address is respectively identifiedas the first-order digit through the"tenth-order digit, wherethefirst order is the lowest or penny digit and the tenth order is the highest order digit of the numher or word. The four cores used to store the first-order digit of. a Word which is residing in an address in the memory. are located in the first row through the fourthrow, counting from bottom to top. The four cores used to store. the second-order digit of the word are located immediately above in the fifth through the eighth rows; in thedrawing, only the fifth and eighth rows are shown, rows six and seven being omitted for the sake of simplicity; The four coresused to store the third-order digit are located immediately above in rows nine through twelve, where rows nine and twelve are the only ones illustrated, rows ten and eleven being omitted for the reasons just mentioned. The location of each higher-order digit progresses upward, as just described, so that the tenth or highest-order digit is located at the top of the column in the last four rows shown; i.e., thirty-seven through forty. Therefore, it is seen, the maximum storage in each memory address is a ten-digit number which will hereinafter be called a word, the lowest-order digit thereof being located at the bottom of each address and the highest-order digit thereof being located at the top of each address.

As the instant computer utilizes the well-known binarycoded decimal-digit system of numerical representation, each of the four cores in a group making up a particular order decimal digit of the word is known as a binary-bit.

The binary-bits are consecutively labeled (a), (b), (c), and (d), where bit (a) is the lowest-order bit represented by the magnetic state of the cores located in rows #1, #5, #9, and #37, and bit (d) is the highest-order bit represented by the magnetic state of the cores located in rows #4, #8, #12 and #40. As previously mentioned, each group of four cores is capable of representing a particular order numerical digit having a value from 0 through 9. For example, to represent a decimal digit having a value of 0. all of the four cores in a group are selectively set to binaryv bit representations (0000); for a decimal digit having a value of 1, the cores are set to (0001) binary bit representations; a decimal digit having a. value of 2, the cores are set to bit representations (0010); a 3 is represented by (0011); 4 by (0100); 5 by (0101); 6 by (0110); 7 by (0111); 8 by (1000); and finally, to represent a decimal digit having a value of 9, the cores are sequentially set to binary bit representations (1001).

To illustrate, supposing that the word 0000000695 is storedin memory at address In the leftmost vertical column, the four lowermost cores, indicated by reference numerals 885 through 888, are respectively conditioned to collectively represent binary bits (0101) indicative of the first-order digit 5. In other words, core 885, representative of binary bit a, is set to binary 1-; core 886, representative of binary bit b, is also set to binary 0; core 887, representative of binary bit 0, is set to binary 1; and, finally core 888, representative of bit d, is setto binary }0 representation. Collectively, the magnetic state ofcores 885 through 888 represents the penny digit 5. The next groupof four -cores,,located directly above group 885 through 888, are set to binary bit representations-(l) and collectively represent the second-order decimal digit 9. The next group of four cores are set to binary bit representations (0110), collectivelyrepresentingnthe third-order. decimal digit- 6. All of the remaining core in addressed are individually set to binary 0 representationsThus, with the non-significant decimal digits removed, the Word becomes 695. a

In one mode of operation, when a column of cores is to be read out to determined the word stored inthat particular memory address, 'the cores are sequentially read, one at a time, starting with the core at the bottom of the address and concluding with the core at the top of theaddress. For example, in address core 885 is read first to produce the binary value of bit a of the firstorder digit; core 886 is read next to produce bit b of the first-order digit; core 887 is read next to produce bit 0; and core 888 is next read to produce bit d of this digit. The next four bits, representing the second-order digit, are successively read out, and the remainder of the bits for successive higher-order digits are thereafter sequentially read out in the same sequence, concluding with bit d of the tenth order decimal digit.

After a core has been read out, it is generally desired to restore the core to its original magnetic state as before being read. That is, after each bit-representing core is readout,v if the core was originally set to represent a binary 1, the core is returned to the 1 state following reading thereof. Therefore, following the reading of each-bit, a predetermined unit of time is permitted to lapse before the next bit is read out; it is during this time lapse that the core, just read, is returned to the 1 state if it had previously been set to that state.

For the sake of simplicity of the following description, the vertical or column orientation of the memory will hereinafter be termed the Y direction, and the horizontal or row orientation will hereinafter be termed the X direction.

Even though, in reality, each of the memory cores has five conductors threaded therethrough for purposes to be more fully described hereinafter, only three of these conductors are to be considered at this time in describing a mode of operation of the memory in terms of the electrical schematic diagram thereof shown in FIG. 2. The first of the three just-mentioned conductors is a sense winding 871, which starts at terminal 872 at the lower left corner of the memory and is alternately threaded through each row of cores bounded by address 5 through 99. As shown, sense winding 871 is successively threaded from left to right through all of the cores of the first row, is threaded from right to left through the cores of the second row, from left to right through the third row, and alternately continues on from row to row. Finally, sense winding 871 is threaded from right to left through the topmost or fortieth row of cores, and terminates at terminal 873. All of the cores in address 5 5 are threaded in the Y direction by common current-carrying conductor 873, which is shown positioned to the left Within the apertures thereof. Also, all of the cores located in the first row bounded by address 5 5 and address B are threaded in the X direction by a common current-carrying conductor 879, which is shown centrally positioned within the apertures thereof, address B being the rightmost one of the memory addresses.

It will now be assumed that it is desired to read out the contents of address 5 5. Thus, in order to read bit a of the first-order decimal digit of the word stored in address a half-amplitude or half-select current impulse is delivered to conductor 878, and, simultaneously there with, a half-select current impulse is present in conductor 879. The two half-select impulses are in such directions that the magnetomotive forces associated therewith are additive in the region of core 885, with the resultant force being of sufficient magnitude to magnetically saturate the core in a direction indicative of a binary zero. Due to the fact that core 385 is the only core in the entire memory that has received the necessary magnetomotive force to cause a reversal of its magnetic state, all of the remaining cores essentially remain magnetically undisturbed. It is known that whenever the state of magnetic remanence of any one of the memory cores is reversed, a voltage impulse is induced thereby in sense winding 871. However, due to the fact that in the present memory only one core at a time is sensed, there is no ambiguity as to which core was responsible for the impulse induced in the sense windmg.

Therefore, if core 885, whose magnetic state is indicative of bit a of the first-order digit of the number, is storing a binary 1, its magnetic state is reversed by the coincidental X and Y read impulses, and, consequently, a voltage impulse appears between terminals 8724573 of the sense Winding 871, indicating that core 885 was previously storing a binary 1. If core 835 had previous ly been storing a binary 0, however, a voltage impulse does not appear across the output terminals of the memory sense winding, thus indicating a binary 0 storage.

After core 885 has been read, its magnetic state is thereafter indicative of a binary 0, as previously mentioned. Thus, if the magnetic state of the core was indicative of a binary 0 before being read, there is no need for resetting the core after it is read. However, if the state of the core was indicative of a binary 1 before being read, it is often necessary to reset the core to a binary l representation after it has been read. To do this, the directions of both of the current impulses applied through the X and Y conductors are effectively reversed simultaneously. This causes a corresponding reversal of the additive magnetomotive force in the vicinity of the core, which reverses the magnetic state thereof. Again, as only a half-select current impulse is applied to each of the X and Y conductors, core 835 is the only core in the entire memory that is magnetically afiected thereby.

Now that core 385 has been read and afterwards reset to its initial state, core 836 is read next to determine the binary value of the bit I? of the first-order digit of the word. Again, a half-select current impulse is applied in the Y direction to conductor 878, and, essentially, a

half-select current impulse is simultaneously applied in the X direction to the conductor of the second row corresponding to 879. As before, both half-select currents are in such directions to effect storage of a binary O in core 886. if the state of core 8% was indicative of a 1 before being read, the current in each of the X and Y conductors threaded theret-hrough is reversed to reset core 886 to 1 after it is read. This reading and writing sequence of operation is sequentially continued from core to core until all forty cores of address have been read and thereafter restored to their respective magnetic states.

The just-described combined readin and writing cycle of operation of each core is hereinafter called a readwrite cycle. The time required to complete a read-Write bit cycle in the instant computer is approximately 40 microseconds. During the first 30 microseconds of the read-write cycle, the core is set to binary O representation; during the remaining 10 microseconds of the cycle, the core is often reset to a binary 1 representation if it was originally in that state. However, if the core was originally in a binary 0 state before being read, there is no resetting operation necessary during the last 10- microsecond interval. Therefore, to read out an entire ten-digit word from an address in memory requires a total time of 40x40, or 1,600 microseconds.

Due to the fact that, in the present memory, it is not desired to reverse the current flow in a conductor, an additional conductor is individually threaded in the X direction through each of the rows of cores. This is illustrated by conductor 880, shown threaded through the cores of the first row and disposed parallel with respect to conductor S79, previously described. By the same token, an additional conductor is also individually threaded in the Y direction through the cores of each of memory addresses 5 5 through 99, and also addresses A and B. This conductor is illustrated by conductor 881, shown threaded through the cores of address 4 and disposed parallel with respect to conductor 8'78, previously described. Thus, two conductors are threaded in the X direction and two conductors are threaded in the Y direction through each of the cores of the memory; each of the four Wires transmits current in only one direction, as will be shown hereinafter. The fifth wire through memory cores in addresses 4 through 9% is sense wire 871, heretofore described. A separate sense winding 891, which originates at terminal 892 and terminates at terminal 393, is alternately threaded, in one direction and then the other, through the forty rows of cores making up memory addresses A and B in the same manner as memory sense winding 871.

Before attempting to give a more detailed description of the memory, it is to be appreciated that each of the rows of cores, from the first to the fortieth row, is connected in the same circuit configuration with respect to the others. Likewise, each of the columns of cores, from addresses through 99 and including addresses A and B, is also of the same circuit configuration with respect to the others. Thus, a description and full cornprehension of the mode of operation of the address 5 5 with respect to the first row of cores for producing bit a of the first-order digit of the word stored in address should suifice for the remaining bits of that digit, and also remaining digits of that word. As the mode of operation of address 3 5 is exactly the same as that of the remaining memory addresses, a further description of the remaining addresses, again, would result only in unnecessary repetition. It is also to be appreciated that, in an attempt to simplify the schematic representation of the memory as shown in FIG. 2, addresses through 59 are consecutively shown, reading from the extreme left to the right; addresses 14 and 19 are shown next, with addresses 11 through 18 being omitted, as indicated by the vertical break in the drawing between addresses 1 5 and 19; following in sequence are addresses 7 2, 29, 31, 39, 4e, 49, 5e, 59, 64:, 69, 7 79, 8e, 89 and 9 5 through 99, and finally addresses A and B; addresses 21-28, 31-38, 41-48, 51-58, 61-68, 71-78, and 81-88 are omitted. Starting from the bottom of the drawing, the first four rows are shown which make up the low-order digit of the word stored in memory; rows #5 and #8 are shown next, with rows #6 and #7 omitted as indicated by the horizontal break in the drawing be tween'rows #5 and #6; following in sequence are rows #9, #12, 13#, #16, #17, #20, #21, #24, #25, #28, #29, #32, #33, #36 and #37 through #40, rows #11, #14-#15, #1s-#19, #22-#23, #26-#27, #30- #31, and #34#35 are omitted.

With particular attention directed to the first row of cores, on emergence from the rightmost end of the first row of cores, conductor 880 is connected to conductor 882, which passes below the first row and is connected at its opposite end to line XDa, located at the bottom left corner of the memory. The leftmost end of conductor 879 also is connected to line XDa, and its opposite end is connected to the cathode of one of crystal diodes 876, its anode being connected to line XG; and, finally, the remaining left end of conductor 880, on emergence from the leftmost end of the first row of cores, is connected to the cathode of one of crystal diodes 877, whoseanode is connected to line (XG}'.

Whenever line XDa is activated, that line is efiectively connected to a source of potential of approximately 12 volts. Thus, if line XG is simultaneously activated therewith, that line is effectively connected to terminal 843 of a temperature-compensated current regulator so that a half-select drive current impulse flows from line XG through diode 876 from right to left through conductor 879 and out at line XDa. However, if line (XG) is simultaneously activated instead of line XG, line (XG) is effectively connected to terminal 843 of the current regulator, so that a half-select current impulse from line (XGqi)' flows through diode 877, thereafter flows from left to right through the upper loop of conductor 880, and is returned to line XDa by way of conductor 882. Consequently, it is seen that, when line XDa is activated, the half-select drive impulse flows in one of two directions through the cores of the first row, depending upon whether XG or (XG)' was simultaneously activated with line XDa.

The electrical connections for rows #2 through #4, respectively representing bits b, c, and d of the first-order digits of the words stored in memory, are exactly the same as for row #1, the anodes of the four crystal diodes 877 each being connected to line (XG)' and the anodes of the four crystal diodes 876 being connected to line XGcp. When line XDb is activated, the line is effectively connected to a potential source of -12 volts, as was line XDa. Thus, when line XG is activated simultaneously with XDb, the half-select current impulse flows from right to left through the cores of the second row; if (XG)' is activated instead of XG, a half-select current impulse flows from left to right through the cores of the second row. By the same token, if XDc and XG are simultaneously activated, a half-select current impulse flows from right to left through the third row of cores; a simultaneous activation of XDc and (XG)' eifectively causes a reversal of current flow through the third row of cores. Finally, XDd and X6117, or XDd and (XG)' operate together to eflectively send a half-select impulse from right to left or from left to right, respectively, through the fourth row of cores in the same manner as just described.

As just described, the first four of diodes 877 (i.e., the ones respectively associated with rows #1 through #4) have their anodes connected together and returned to lines (XG)'. The second group of four diodes 877, associated with rows #5 through #8, of which only rows #5 .and #8 are illustrated, all have their respective anodes connected to line (XG1)'. The anodes of the V 8 third group of diodes are each connected to line (XG2)', the anodes of the fourth group being connected to (XG3)', and so on up the column, with the anodes of the tenth group of diodes 877 being connected to line (XG9). Also, as shown, the left end of each of the conductors corresponding to 879 and 882 associated with rows #1, #5, #9, #13 #33, and #37, which rows successively correspond to bit a of each successive-order decimal digit of the word stored in memory, are connected together and returned to line XDa. Likewise, although not fully illustrated, the left end of each of the conductors corresponding to 879 and 882 but associated with rows #2, #6, #10, #14 #34, and #38, which rows successively correspond to hit b of each successive-order decimal digit of the word in memory, are connected together and returned to line XDb. By the same token, although not fully illustrated, the left end of each of the conductors corresponding to 879 and 882 but associated with rows #3, #7, #11, #15 #35, and #39, which rows successively correspond to hit c of each successive-order decimal digit of the word in memory, are connected together and returned to line XDc. And finally, .the left end of the conductors corresponding to 879 and 882 but associated with rows #4, #8, #12, #16 #36, and #40, which rows successively correspond to bit d of each successiveorder decimal digit of the word in memory, are connected together and returned to line XDd.

With respect to the vertically-disposed column of diodes located to the right of address B and indicated as 876, the first bottom group of four diodes thereof associated with rows #1 through #4 each has its anode connected to line XGnS; the second group of four diodes 876 located directly above the first group have their anodes returned to common line XG-l; the anodes of the third group of diodes 876 are connected to line X62, and so on, with the anodes of the last four diodes 876 at the top of the column and associated with rows #37 through #40 being connected to common line XG9.

Referring to the lowermost row of diodes 874 located below row #1, counting from left to right, the anodes of the first ten of diodes 874 respectively associated with addresses through 9 are connected to line YGqs. With respect to the next group of diodes 874 located immediately to the right of the first group of diodes and respectively associated with addresses 11 through 19, of which only addresses 11 and 19 are illustrated and addresses 12 through 18 are omitted, their anodes are connected to line YGl; the anodes of the third group of diodes 874 respectively associated with addresses 20 through 29 are connected to line YG2; and so on, with the anodes of the last group of ten diodes 874, respectively associated with addresses 9d through 99, being connected to line YG9. With respect to the upper row of diodes 875, which are located directly above row #40, the first group of ten diodes which are respectively associated with addresses through 99 have their anodes connected to line (YG)' in the same manner as the lower row of diodes 874. The anodes of each successive group of ten diodes 875, counting from left to right, are respectively connected to lines (YG1)' through (YG9).

To complete the electrical connections to memory addresses through 99, the upper ends of vertical conductors corresponding to 878 and 883, which are respectively associated with addresses 'lqb, 2qb, 3 8, and 9 5, are connected to line YD. The upper ends of vertical conductors corresponding to 878 and 883, which are respectively associated with addresses 01, 11, 21, 31 81, and 91, are connected to line YDl. Only addresses l and 91 of this group are illustrated, the remaining addresses of this group being omitted for simplicity purposes. Likewise, the upper ends of vertical conductors 878 and 883, which are respectively associated with addresses e2, 12, 22, 32 82, and 92 are connected to line YDZ. This sequence of connections continues from lines YD3 through YD9, where YD9 is connected to vertical conductors corresponding to 878 and 383, which are respectively associated with addresses e9, 19, 29, 39 89, and 99.

To summarize: Selective energization of line YD essentially selects all addresses whose low-order digit is a YD} essentially selects all addresses whose loworder digit is a 1; H32 essentially selects all addresses whose low-order digit is a 3; and so on from YD-S through YD9, where YD9 essentially selects all addresses whose low-order digit is a 9. Forgetting about primenotations for the present, selective energization of line YG essentially selects all addresses whose high-order digit is a 0; YGl essentially selects all addresses whose high-order digit is a 1; YG2 essentially selects all addresses Whose high-order digit is a 2; and so on from YG3 to YG9, where selective energization of line YG9 essentially selects all addresses whose high-order digit is a 9. Thus, suppose that it is desired to select a particular address; say address 9 5. To accomplish this, YD is energized corresponding to the low-order digit 0 of the address, and, simultaneously therewith, YG9 is energized corresponding to the high-order digit 9 of the address. Thus, when YD and YG9 are simultaneously energized, a binary 1 representative half-select current flows upwardly from line YG9 through all of the cores in address 9 5 and out at line YDe. To select address 99, YD9 and Y G9 are energized simultaneously.

As far as prime notations are concerned, it is to be pointed out at this time that throughout the electrical circuitry of the computer signal lines bearing a prime notation-i.e. (XG) and (YGqb)' et al.-essentially have diametrically opposite states or energization conditions to their respective primeless counterparts; i.e., XG, YGqb, et. 'al. For example, lines (YG) through (YG9) are eifective to selectively send a half-select drive-current impulse downwardly through any one of addresses on through 99 to half-select a particular address to a binary O representation, whereas lines YG through YG9 are effective to send a half-select impulse upwardly through any one of the same respective addresses to half-select that particular address to a binary 1 representation. It is also to be appreciated at this point that, when the state of a signal line bearing a prime notation is de-energized or is FALSE, the primeless signal line counterpart is respectively energized or is TRUE, and vice versa. In other words, when one is energized, the other is de-energized; when one is TRUE, the other is FALSE, etc.

In the X direction of the memory, line XDa selects those ten rows corresponding to bit a of each order decimal digit of the word; line XDb selects those ten rows corresponding to bit b; line XDc selects the ten rows corresponding to bit 0; and, finally, line XDd selects the final ten rows corresponding to bit d of each order decimal digit of the word. Lines (XG)' through (XG9)' are erTective to send a half-select drivecurrent impulse from left to right through any one of rows #1 through #40 to half-select a particular row to a binary 0 representation, whereas lines XG through X69 are effective to send a half-select impulse from right to left through any one of the same respective rows to halfselect that particular row to a binary l representation.

Thus, combining X and Y selection of the memory, in order to store a binary l representation in a core, say core 835 as an example, which is located at the junction of row #1 and address gbgb, lines YD, YG, X1311, and XGe are all simultaneously energized. To store a binary 0 representation therein, lines YD (YG)', XDa, and (XG) are all effectively energized simultaneously. To store binary information in core 886, line XDb is energized instead of line XDa. The manner of X and Y selection of addresses A and B is exactly the same as the manner of selection of memory addresses through 99. Consequently, further detailed description thereof is not deemed necessary.

Before proceeding further with the description of the logical control circuitry of the computer, it is to be pointed out that an attempt has been made to simplify and thus alleviate the inherent complexity of the schematic representation in order to facilitate a full and complete understanding of the circuitry, bot-h as to its organization and as to its mode of operation. For example, throughout the drawings, all input lines are appropriately labeled and are positioned to the leftmost side of the various building blocks previously described, and the various output lines thereof also are appropriately labeled and are positioned to the rightmost side of the building blocks. However, for illustrative purposes only, but a se lected few of the input and output lines are actually shown connected. It is, of course, to be understood that, in order to obtain a full and complete electrical circuit diagram of the computer, it first is necessary to substitute the appropriate type of building block circuitry (taken from FIGS. 46 through 51 of the aforementioned Patent 3,112,394) for each of the correspondingly-labeled building blocks which are logically illustrated throughout the drawings. Afterwards, all like-labeled lines (whether input lines, output lines, or otherwise) are to be connected together, thus forming a complete circuit diagram from the schematic representation thereof.

X -drivers VJith reference to the lower right-hand section of FIG. 3, there are schematically illustrated four X-drivers, which are utilized to selectively energize input lines XDa through XDd, previously described in connection with the core memory shown in FIG. 2. Each of the X-drivers comprises a two-input logical AND of type R1, an inverter amplifier of type I12, and an emitter follower amplifier of type E3, each connected in cascade with respect to the others. More specifically, the X-driver for bit (1 includes logical AND 11%, inverter 4237, and emitter follower 425%; the X-driver for bit b comprises logical AND 1169, inverter 4233, and emitter follower 4251; the X-driver for bit 0 comprises logical AND 1110, inverter 4239, and emitter follower 4252; and, finally, the X-driver for bit d comprises logical AND 1111, inverter 4249, and emitter follower 4253.

During a read-write cycle of operation for reading a word from an address in memory, line SMC goes TRUE for 1600 microseconds to allow line XDW to effectively condition the selected X-driver to effectively be turned ON at, and for, the proper amount of time. At 40 microsecond intervals, lines Bah f through Ba'M sequentially go TRUE for a period of 40 microseconds each, and then respectively go FALSE. Consequently, at the beginning of the read-write cycle, output line XDa is energized, and a potential of approximately 12 volts appears thereon. Line XDa stays energized for a maximum period of 40 microseconds and then is de-energized. Forty microseconds after line XDa was first energized, output line XDb is energized for a maximum period of 40 microseconds, and then is de-energized. Forty microseconds after line XDb was first energized, line XDc is energized for a maximum period of 40 microseconds. Finally, 40 microseconds after line XDc was first energized, line XDd is energized for a maximum period of 40 microseconds, lines XDa through XDd of FIG. 3, of course, being identical to lines XDa through XDd of FIG. 2, as previously stated. Thus it is evident, as a maximum total time of microseconds is required to read each digit out of memory, that a maximum time of 1600 microseconds is required to read a ten-digit number out of a particular address in memory.

Bit-counter The bit-counter, logically shown in the upper portion of FIG. 5, includes two type F2 flip-flops 6041 and 6042, connected as a scale-of-four binary counter, and is utilized to select the binary bit of the word to be read out of an address in memory during a read-write cycle, as illustratedin the block diagram of FIG. 1. When the computer is first turned ON flip-flops 6041 and 6042 are unconditionally set TRUE by reset line (RS)' going FALSE. That is, the states of flip-flops 6041 and 6042 are such that reference output lines BCa and BCb, respectively therefrom, are TRUE, and prime outline lines (BCa)' and (BCb)' are both FALSE.

The bit-counter usually counts in a forward direction, as will be shown later. However, there are times when the bit-counter is required to effectively count in a reverse direction. When counting in a reverse direction, the read-write word cycle begins by reading out the highorder bit of the high-order digit; i.e., bit d of digit #9. The signal which provides for this reverse operation of the bit-counter comes from line DBD. When line 'DBD is TRUE (line (DBD) thus being FALSE), the bit-counter counts in a reverse direction. Conversely, when .line DBD is FALSE (line DBD) thus being TRUE), the bit-counter counts in a forward .direction. 7

If it be desired that the bit-counter is to count in a forward direction, lines (DBD), BCa, and BC!) must first be TRUE. Therefore, as all three inputs to logical AND 1158 are simultaneously TRUE, lines Ed and BdM are also TRUE, the remainder of output lines Ba through Ba and BaM through BdM being FALSE. When input line CYC goes from TRUE to FALSE, the prime inputs to 7 both of flip-flops 6041 and 6042 go from TRUE to FALSE. Consequently, both flip-flops 6041 and 6042 change state, so that lines BCa and BCb go FALSE and lines '(BCa)' and (BCb)' go TRUE. As lines (DBD), (BCa), and (BCb)' are now TRUE, all of the inputs to logical AND 1152 are simultaneously TRUE, and thus output line Ba is TRUE, with the remaining outputs Bb through Bd being FALSE. When line CYC goes from FALSE back to TRUE, the state of both flip-flops remains unchanged. However, when line CYC again goes from TRUE to FALSE, the reference input to flip-flop 6041 goes from TRUE to FALSE. At this time, lines HQ: and (BCb) are TRUE, and lines (BCa) and BCb are both FALSE. Thus, as inputs (DBD), BCa, and (BCb)' of logical AND 1154 are simultaneously TRUE, output line Bb is TRUE, and remaining outputs Ba, Bc, and Ed are FALSE. When line CYC goes from TRUE to FALSE a third time, all input lines to logical AND 1156 are simultaneously TRUE, and output line Be is likewise TRUE,

with lines Ba, Bb, and Ed being FALSE. Finally, when CYC goes from TRUE to FALSE a fourth time, line Ed is TRUE, with lines Ba through Bc being FALSE.

To summarize, only readout line Ed is initially set TRUE when the computer is first turned ON, the remaining readouts, Ba through Bc, are FALSE. At this time, for each successive occurrence of a TRUE-to- FALSE reversal of line CYC, the bit-counter is incremented by a count of one binary bit. Thus, with four such reversals of line CYC, the bit-counter counts Ba, Bb,

Be, and back to Ed. When the bit-counter is to count backwards, line DBD is rendered TRUE instead of line (DBD). Consequently, at this time, line Ba instead of line Ed is TRUE; remaining lines Bb through Bd are FALSE. Thereafter, for each successive occurrence of a TRUE-to-FALSE reversal of line CYC, the counter is 12. X and Y Grounders In the left portion of FIG. 9, there are diagrammatically shown two sets of ten X-grounders, one set of ten represented by output lines XG through X69, and the other represented by output lines (XG) through (XG9). Each of the twenty X-grounders comprises a serially-connected network of a two-input logical AN-D of type R1, an inverter amplifier of type I12, and an The Y-grounders shown in the right section of FIG. 9 are of essentially identical circuit configuration to the justdescribed X-grounders, and, as their mode of operation is also essentially the same as that of the X-grounders, a detailed description thereof would result in unnecessary repetition. The prime difference between the X and Y- .grounders is that lines WR and (WR)' are individually AN-DED with lines DM, D1 thronghDS, and D9M for the X-grounders and individually ANDED with lines Wlqb through W19 for the Y-grounders, lines DqbM, D1 through D8, and D9M being the output leads of a digit counter to be described next.

Digit counter With reference to FIG. 6, there is shown a scale-of-ten binary counter, herein called a digit counter, which is utilized, among other purposes, to select a particular order digit of the word stored in an address in memory. The digit counter includes four type F2 fiipflops 6043 through 6046 effectively connected in cascade in a manner such that, each timeline AD goes from TRUE to FALSE, the following takes places: flipflop 6043 changes state; except during a so-called recycling mode .of operation, which will be described hereinafter, flipflop 6044 changes state if the state of line Da goes from TRUE to FALSE; flipflop 6045 changes state if the state of line Db goes from TRUE to FALSE; and flipflop 6046 changes state if the state of line Dc goes from TRUE to FALSE.

For example, for a count of 0, flipflops 6043 through 6046 are in a FALSE state; that is, their states are such that lines Da through Dd are FALSE and lines (Da)' through (Dd)' are all TRUE. If it is desired for the digit counter to count in a forward direction (i.e., 0, 1, 2, 3 7, 8, 9), line (DBD) is selectively set TRUE. After flipflops 6043 through 6046 are set FALSE, all of the inputs to logical AND 1178 are simultaneously TRUE. Thus, readout line 13 is also TR-UE and thereby represents a count of 0. Thereafter, the first time line AD goes from TRUE to FALSE, flipfiop 6043 changes state, and line D1, at that time, is the only readout line that is TRUE, thus indicative of a count of 1. The second time line AD goes from TRUE to FALSE, flipfiops 6043 and 6044 both change states, so that line D2 is TRUE, with the remaining readout lines being FALSE. The counting continues until a count of 9 has been reached, as indicated by lines Da and Dd being TRUE. Thereafter, the next time line AD goes from TRUE to FALSE, flipflops 6043 and 6046 both change state, so that lines Da through Dd are thereafter FALSE and lines (Da)' through (Dd)' are tbhereafter TRU E, thus representing the .original count of K .97

When the computer is first turned ON, the digit 

1. IN A MACHINE OF THE CLASS DESCRIBED HAVING A MAGNETIC MEMORY SYSTEM OF THE TYPE INCLUDING A PLURALITY OF MAGNETIC STORAGE ELEMENTS ARRANGED IN AN OPERATIVE ROW AND EACH OF WHICH POSSESSES A SUBSTANTIALLY RECTANGULAR HYSTERESIS LOOP CHARACTERISTIC AND CAPABLE OF BEING MAGNETICALLY SATURATED IN ONE OR THE OTHER OF TWO OPPOSITE MAGNETIC POLARITIES, A FIRST COIL INDUCTIVELY COUPLED TO ALL OF SAID STORAGE ELEMENTS, AND A PLURALITY OF SECOND COILS EACH OF WHICH IS INDUCTIVELY COUPLED TO A DIFFERENT ONE OF SAID STORAGE ELEMENTS, IN WHICH SYSTEM EACH EVENNUMBERED STORAGE ELEMENT OF SAID ROW IS MAGNETICALLY SATURATED OF A FIRST MAGNETIC POLARITY REPRESENTATIVE OF INFORMATION OF A FIRST TYPE AND IS MAGNETICALLY SATURATED OF A SECOND MAGNETIC POLARITY REPRESENTATIVE OF INFORMATION OF A SECOND TYPE, AND IN WHICH SYSTEM EACH ODDNUBERED STORAGE ELEMENT OF SAID ROW IS MAGNETICALLY SATURATED OF SAID SECOND MAGNETIC POLARITY REPRESENTATIVE OF INFORMATION OF SAID FIRST TYPE AND IS MAGNETICALLY SATURATED OF SAID FIRST MAGNETIC POLARITY REPRESENTATIVE OF INFORMATION OF SAID SECOND TYPE, MEANS FOR DETERMINING THE POLARITY OF MAGNETIZATION OF EACH OF SAID STORAGE ELEMENTS WHILE MINIMIZING UNDESIRED READ-OUT VOLTAGES COMPRISING: A SENSING COIL INDUCTIVELY COUPLED TO ALL OF SAID STORAGE ELEMENTS; ADDITIONAL MEANS TO MAGNETICALLY SATURATE ALL OF SAID STORAGE ELEMENTS IN ALTERNATING MAGNETIC POLARITIES WITH RESPECT TO ADJACENT ONES, ONE AFTER THE OTHER IN A SEQUENTIAL MANNER STARTING WITH THE STORAGE ELEMENT TERMINATING ONE END OF SAID ROW AND ENDING WITH THE STORAGE ELEMENT TERMINATING THE OPPOSITE END OF SAID ROW; MEANS RESPONSIVE TO SUBSTANTIALLY AN ABSENCE OF INDUCED VOLTAGE IN SAID SENSING COIL DURING SATURATION OF A SELECTED STORAGE ELEMENT BY SAID ADDITIONAL MEANS, INDICATIVE OF THE SELECTED STORAGE ELEMENT HAVING BEEN PREVIOUSLY SATURATED OF THE SAME MAGNETRIC POLARITY, TO CAUSE ALL OF SAID STORAGE ELEMENTS TO BE PARTIALLY DRIVEN TOWARD THE OPPOSITE SATURATION POLARITY AS THAT OF THE SELECTED STORAGE ELEMENT; AND MEANS RESPONSIVE TO AN INDUCED VOLTAGE IN SAID SENSING COIL DURING SATURATION OF A SELECTED STORAGE ELEMENT BY SAID ADDITIONAL MEANS, INDICATIVE OF THE SELECTED STORAGE ELEMENT HAVING BEEN PREVIOUSLY SATURATED OF THE OPPOSITE MAGNETIC POLARITY, TO CAUSE ALL OF SAID STORAGE ELEMENTS TO THE PARTIALLY DRIVEN TOWARD THE OPPOSITE SATURATION POLARITY AS THAT OF THE SELECTED STORAGE ELEMENT AND TO ADDITIONALLY CAUSE THE SELECTED STORAGE ELEMENT TO BE SATURATED OF THE OPPOSITE MAGNETIC POLARITY, WHEREBY THE SELECTED STORAGE ELEMENT IS RESTORED TO ITS ORIGINAL SATURATION POLARITY THEREBY PRESERVING THE INFORMATION REPRESENTED B THE SATURATION POLARITY THEREOF. 